1. Field of the Invention
The present invention relates generally to a double link type suspension system, for example, in use for an automotive vehicle, and more particularly to a double wish-bone type suspension system having upper and lower control arms and a shock absorber whose one end is attached to the side of a vehicle body and whose other end is connected directly or through the lower control arm to a steering knuckle.
2. Description of the Prior Art
In connection with automotive vehicles, a variety of double link type suspension systems have been proposed and put into practical use as disclosed, for example, in Japanese Patent Provisional Publication No. 59-96007 (referred hereinafter to as "the first prior art") and in Japanese Patent Provisional Pubrication No. 60-135314 (referred hereinafter to as "the second prior art"). In a suspension system of the first prior art, an upper section of a knuckle is upwardly extended over a wheel to form an upper end thereof, in which the upper end is connected through an upper control arm to a vehicle body. In a suspension system of the second prior art, an upper control arm is long as compared with as usual, and a steering axis (kingpin axis) is set regardless of the upper control arm. Now in order to obtain a suitable suspension geometry, the upper control arm of the double link type suspension system is required to ensure a considerable length and therefore cannot be so shortened.
The above-summarized prior art will be discussed hereinafter. In the case of the first prior art suspension system, the inboard end of the upper control arm is supported by a vehicle body while the outboard end of the same is connected to the upper end of the knuckle, and additionally the upper control arm cannot be shortened for the above-mentioned reason, thereby allowing a wheel house to extend to the side of an engine compartment in accordance with the length of the upper arm. In addition, a shock absorber is disposed generally parallel with the upwardly extended knuckle upper section. Thus, the width of the wheel house is enlarged thereby to unavoidably minimize the width of the engine compartment. Particularly in this first prior art suspension system, since the knuckle which is disposed parallel with the shock absorber is turned together with the wheel during steering, a sufficiently wide space is necessary between them in order to prevent interference therebetween during turning of the vehicle. This particularly enlarges the width of the wheel house. Furthermore, the turning of the knuckle together with the wheel requires a ball joint large in height for connection between the upper end of the knuckle and the upper control arm, so that the height of the wheel house is unavoidably enlarged.
In the case of the second prior art suspension system, the distance between the upper and lower control arms is relatively small, variation of camber angle and caster angle due to assembly error of suspension system component parts ends up being relatively large. Additionally, such camber angle and caster angle change greatly depending upon the vertical swing of the upper and lower control arms. Therefore, the vehicle steering is not sufficiently controllable.